Himalayan Monal is raising its voice to be heard over human noise, study finds
Dehradun: The Himalayan monal, Uttarakhand’s state bird, is calling at higher frequencies in parts of the Himalayas where traffic, tourists, pilgrims and other human activity have made the landscape noisier.
Researchers at Hemvati Nandan Bahuguna Garhwal University recorded 719 monal calls between April 2023 and June 2024, comparing a relatively quiet stretch of Madmaheshwar Valley with the busier Chopta Valley in the Kedarnath Musk Deer Sanctuary.
Published in Behavioural Processes in August 2025, the study by Rajeev Lochan, Dinesh Kumar Sharma and Anand Kumar found that in the noisier landscape, the birds produced calls with higher peak frequencies and slightly longer durations.
At the median level, the peak frequency in the quieter habitat was around 171 Hz lower than in the noisier habitat. The difference was strongest at the upper end of the birds’ vocal range, where the model explained about 73.4% of the variation.
The likely reason is acoustic masking — when background noise overlaps with an animal’s signal and makes it harder to detect. Human noise from roads and vehicles can occupy frequencies used by wildlife. The monal appears to be shifting its calls higher to cut through the noise.“A call helps a bird communicate, find mates and defend its territory. So when that call changes, it is worth paying attention,” the study notes. The finding suggests human-generated noise is reaching deep into the monal’s habitat.
The two valleys offered contrasting soundscapes. Madmaheshwar has relatively little human activity and no road. Chopta, within the Kedarnath Musk Deer Sanctuary, sees regular vehicles, pilgrims, trekkers and birdwatchers. Calls were captured using directional microphones and AudioMoth recorders during morning and evening hours.
The study does not establish that the changed calls are affecting mating success or population, nor that birds can compensate indefinitely. It also leaves open whether altered calls carry behavioural or physiological costs.
The concern comes as other pressures mount. In a separate 2025 study in Scientific Reports using 5,122 occurrence records, the same team found that under one climate scenario, more than 14% of currently suitable monal habitat — alpine and subalpine areas, oak-mixed forests and rhododendron slopes between 2,400 and 4,500 metres — could become unsuitable by 2041–2070.
The monal is currently classified as Least Concern on the IUCN Red List, but researchers say global status does not capture local changes in how the bird lives and communicates in an increasingly loud Himalaya.
